It is the ordinary method of frying with conventional fryers to heat frying oil in a fryer and put the material to be fried into the oil after the oil has been heated to a suitable temperature for frying. In this method of frying, however, the temperature of the oil decreases as the material to be fried is put into the oil, and further, the oil is gradually oxidized due to the accumulation in the oil of bits of deep-fried batter, making the oil unable to perform frying in the desired way.
The present invention has been achieved through many and various experiments for frying material always in a desired way by eliminating said problems with the conventional fryers, and the invention provides a fryer free of said problems and capable of frying material always in an excellent way.